In general, an underpants-type disposable diaper includes: an outer body forming individually or integrally a front body and a back body; an inner body that has an absorber and is attached to the inner surface of the outer body from the front body to the back body; and the outer body of the front body and the outer body of the back body are joined together at the both side edges to form a waist opening and a pair of right and left leg openings. The underpants-type disposable diaper also generally has leg gathers as parts standing toward the legs of a wearer on width-direction both sides of an absorption surface of the inner body to improve the fit to the legs and prevent lateral leakage (for example, see Patent Documents 1 to 3).
There have been generally proposed leg gathers with various structures. In a currently general structure, the leg gathers have attachment parts that are fixed to the back side of the inner body, extension parts that are extended from the attachment parts to surfaces of side parts of the inner body so as to wrap around lateral sides of the inner body, fallen parts that are formed by fixing front-back both end portions of the extension parts in a fallen state to the surfaces of the side parts of the absorbent article, free parts that are formed by not fixing intermediate portions of the fallen parts in the extension parts, and elastically stretchable gather materials that are fixed in an extended state along a front-back direction to at least forward end portions of the free parts. When the diaper is worn, the leg gathers stand by the contraction of the elastically stretchable gather materials at the free parts to form leakage prevention walls that fit elastically along the legs of the wearer.
The leg gathers are intended to prevent leakage. Therefore, the leg gathers desirably have sufficient water-shielding performance. In addition, the leg gathers are to contact with the wearer's skin and desirably have cloth-like texture. Accordingly, the leg gathers are generally structured to be entirely covered with water-repellent non-woven fabric with favorable texture. In addition, to provide water-shielding performance, a liquid impervious film is contained in the gathers or three-dimensional gathers are provided in a plurality of rows without the liquid impervious film.
Meanwhile, absorbent articles are to thrown away after use, and the control of material costs is one of very important issues. Conventionally, much effort has been devoted to changing the kinds of materials and employing less wasteful (efficient) materials.
However, there is still room for improvement in reduction of the materials for leg gathers. Specifically, with importance placed on the water-shielding performance of the leg gathers as described above, the liquid impervious film needs to be contained in the gathers, but the liquid impervious film is less preferable in texture. Therefore, it is considered that the front and back surfaces of the liquid impervious film need to be entirely covered with non-woven fabric in order to ensure the compatibility between water-shielding performance and favorable texture, and there is no room for improvement in the reduction of materials.